This invention relates to threaded fasteners. More particularly, this invention relates to industrial threaded fasteners having intelligent properties.
Threaded fasteners have long been used to fasten together myriad types of mechanical parts. Some examples of the different types of mechanical parts which can be fastened together by threaded fasteners are structural members, such as bridge girders, support beams in buildings, and aircraft structural members. Typically, during installation each threaded fastener is inserted into an aperture in the piece to be captured and threaded into a designated portion of the mating piece, such as a nut secured to, or a threaded aperture formed in, the mating piece. In many applications, each fastener must be threadably tightened to a specific torque amount within a narrow band of specified tolerances. The specified tolerances are usually part of the specifications created for a given project, and may be presented in paper form or in electronic form (such as stored in a flash drive or other computer-readable memory) for use with a portable computer which can be transported to the job site. Both manual torque wrenches and power driven torque tools are typically used to tighten the fastener to a value lying within the specified torque range. Typically, the installer must consult the specifications in order to determine the proper range of permissible torque values, and then tighten the fastener. Ideally, the installer would manually create a record of each installed fastener by site location and torque value and submit such record to an inspector or other person or office responsible for maintaining project data. However, this is not always done.
Many projects require that the installed fasteners be checked for proper torque value immediately after installation, and later on a regular basis, in order to ensure the safety of the entire structural assembly. This inspection and check must be performed by a qualified person (usually a trained inspector) having an authentic copy of the original specifications, and is usually done manually by the inspector with a torque wrench, a power driven torque tool or a torque measurement device applied to each installed fastener. In addition, the inspector typically conducts a visual survey to determine whether any fasteners are missing. The results of the inspection and check must be reported to the designated person or office which maintains the inspection records for future reference.
Because the inspection process must be manually and visually performed on each individual fastener, the process is very time consuming and subject to human error—e.g., by failing to correctly apply the proper torque specification value to one or more fasteners, failure to accurately measure the torque on a given fastener or failure to notice the absence of a fastener from a designated fastener site. In addition, as noted above, a record of the initial installation of fasteners is not always created to the detriment of those responsible for maintaining the integrity and safety of fastened structures.